The review covers the fifty-year period of chemistry of the closo-decaborate anion [B10H10]2– from the first report by Hawthorne and Pitochelli. The main attention is paid to reactions of substitution of various atoms and groups for hydrogen atoms. The general stability of the closo-decaborate cage, including its protonation, cage-opening and cage oxidation reactions, is considered as well. A review with 242 references.

ABSTRACT:The effectiveness of the interactions between various alkyl ammonium cations and the well-defined spherical Keplerate-type {Mo 132 } capsule has been tracked by 1 H DOSY NMR methodology which reveals a strong dependence of the selfdiffusion coefficient of the cationic guests balancing from the solvated to the plugging situations. Analysis of the data is fully consistent with a two-site exchange regime involving the 20 independent {Mo 9 O 9 } receptors of the capsule. Furthermore, quantitative analysis allowed determining the stability constants associated to the plugging process of the pores. Surprisingly, the affinity of the capsule for a series of cationic guests increases continuously with its apolar character as shown by the significant change of the stability constant from 370 to 6500 from NH 4 + and NEt 4 + , respectively. Such observations, supported by the thermodynamic parameters evidence that the major factor dictating selectivity in the trapping process is mainly the so-called "hydrophobic effect". Computational studies, using molecular dynamics simulations have been carried out in the conjunction of the experimental data. The analysis of the radial distribution functions g(r) reveals that NH 4 + and NMe 4 + ions behave differently in the vicinity of the capsule. The NH 4 + ions do not exhibit well-defined distributions in its close vicinity. In contrast, the NMe 4 + ions were identified as sharp distributions related to different scenario such as firmly trapped or as labile guest facing the {Mo 9 O 9 } pores. These conjugated experimental and theoretical insights should aid the exploitation of these giant polyoxometalates in solution for various applications.

The magnetic properties of the pentacoordinate [M (Me cyclam)N ] (Me cyclam=tetramethylcyclam; N =azido; M=Ni, Co) complexes were investigated. Magnetization and EPR studies indicate that they have an easy plane of magnetization with axial anisotropy parameters D close to 22 and greater than 30 cm for the Ni and Co complexes, respectively. Ab initio calculations reproduced the experimental values of the zero-field splitting parameters and allowed the orientation of the anisotropy tensor axes with respect to the molecular frame to be determined. For M=Ni, the principal anisotropy axis lies along the Ni-N direction perpendicular to the Ni(Me cyclam) mean plane, whereas for M=Co it lies in the Co(Me cyclam) mean plane and thus perpendicular to the Co-N direction. These orientations match one of the possible solutions experimentally provided by single-crystal cantilever torque magnetometry. To rationalize the geometry and its impact on the orientation of the anisotropy tensor axis, calculations were carried out on model complexes [Ni (NCH) ] and [Co (NCH) ] by varying the geometry between square pyramidal and trigonal bipyramidal. The geometry of the complexes was found to be the result of a compromise between the electronic configuration of the metal ion and the structure-orienting effect of the Me cyclam macrocycle. Moreover, the orientation of the anisotropy axes is mainly dependent on the geometry of the complexes.